If pressure sensors, pressure transmitters along with other field equipment are used near flammable gases or dust, they might be subject to marking in accordance with the ATEX product guideline 94/9/EC. ATEX requires the type label of the sensor to add the ATEX marking, so usually that is labelled directly onto the sensor during production.
Close to the Notified Body and the approval number, the marking of pressure sensors also contains important information for an individual. For instance, an ?X? after Simplified indicates that special conditions should be observed with all the device. These are either given in the approval document and in the corresponding manual. Most importantly, marking in accordance with ATEX gives info on the possible areas of application and the sort of protection used for the pressure sensor:
Explosion group:
I Mining industry, II other areas useful Device class:
Used in zone 0/20 near von flammable gases (1G), dust (1D)
Used in zone 1/21 in the vicinity of flammable gases (2G), dust (2D)
Use in zone 2/22 near flammable gases (3G), dust (3D)
However, there are also devices where only certain parts may be installed in other zones, for instance, a pressure sensor marked 1/2G could be installed in a tank with flammable content. The electronic the main transmitter is located on the outside of the tank, and therefore in zone 1.
Examples for forms of protection:
i intrinsic safety (Limitation of electrical ignition energy by limiting current and voltage)
ia for Zone 0 or Zone 20 (for Zone 20 also iaD)
ib for Zone 1 or Zone 21 (for Zone 21 also ibD)
ic for Zone 2 d
flameproof / explosion proof enclosure, ideal for zone 1/21 and 2/22 n
non-incendive, suitable for zone 2/22 m
encapsulation suitable for zone 1/21 and 2/22 Gas group and temperature class: i.e. IIC T1 for hydrogen
Note:
Further information on the subject of hydrogen can be found on the WIKA website. For those who have any further questions, your contact will gladly help you.